Novice yeast harvesting thread

[daf]

Not done this before so any advice will be helpful. I am trying to harvest yeast from my own brews and from bottles. Here is tonight's lot...



MJ West Coast from my galaxy pale ale in the FV, in water for later, same in a DME wort as a starter, and a slug of the dregs of a Shepherd Neame 1689 in the same wort.

[YeastWhisperer]

One should never rinse or store yeast in water. Contrary to what is posted on many home brewing forums, storing yeast in water does not make it go dormant. Storing yeast in water merely starves the culture. Secondly, storing yeast in water is biologically unsound. While green beer is toxic to yeast, it is even more toxic to the organisms that want to infect a culture.

[daf]

Thanks, what shall I put in there then?

[daf]

Hello? Don't suppose you could bring a few solutions to the party along with your problems?

[YeastWhisperer]

First and foremost, one must brew more than one intends to package. I am an American. While I am comfortable working in the metric system (all of my lab work is performed using metric units of measure), I prefer to brew using U.S./English units of measure. My standard brew length is 3.7 U.S. gallons, which is approximately 14 liters. Of that three 3.7 gallons, I leave 0.2 to 0.35 U.S. gallons in the kettle with the break and hops, and 0.35 to 0.5 U.S. gallons in the primary fermentation vessel upon racking. My packaged volume is 3 U.S. gallons, which is little under 11.5 liters. I use the residual green beer that is left in the primary fermentation vessel to swirl the culture back into suspension, wait a few minutes for the break and dead yeast cells to settle, and carefully decant between 250 and 350ml of thin slurry into a sanitized 500ml Erlenmeyer flask after wiping the pouring lip on the fermentation vessel with 70 to 90% alcohol. The goal here is to leave break, particulate matter, and as many dead cells as possible in the fermentation vessel.

As aside, I brew 6 U.S. gallons (23L) when I target 5 U.S. gallons (19L). I leave one-half of a gallon in the kettle with the break and hops and one-half of gallon in the primary fermentation vessel to use for cropping.

Here is a photo of two crops in my brewing refrigerator:




Note: On brew day, I pitch between 3 and 7 milliliters of thick slurry per liter of wort after decanting the supernatant (the clear liquid above the solids) and wiping the mouth of the flask with alcohol. There is no need to make a starter if the crop is less than four weeks old.

[daf]

I'm top cropping it, not taking from the slurry.

http://www.howtobrew.com/section1/chapter6-8.html

[YeastWhisperer]

Top cropping requires a different approach because one wants to take advantage of yeast cells that are a) in optimum health, and b) have not undergone the morphological changes that occur at the end of fermentation in preparation for starvation (yeast cell walls thicken in preparation for quiescence). It is basically impossible to maintain a yeast crop in that state without pitching it within a few days because the yeast cells will deplete their energy stores. The alternative is to collect an equal amount of young beer with the skimmed crop, which is kind of a combination of skimming and krausening. This method provides a nutrient source and a protective environment for the crop. The cells will prepare for starvation and enter quiescence after the carbon (sugar is carbon bound to water) in the young beer has been consumed just as they would at the end of fermentation; however, the crop will be a lot cleaner than bottom cropped yeast. I assume that you are taking a small amount of young green beer with your crop.

[Goulders]

There is a "how to" on top cropping by wolfy in the yeast thread

[daf]

So Palmer is wrong yet again!

[YeastWhisperer]

That's an old release of "How to Brew." If you are using that book as a reference, you are working with nineties home brewing knowledge. Rinsing yeast with and storing it under boiled water is one of the biggest hoaxes played on the home brewing community. It is voodoo passing as science.

From the "Recovering yeast after fermentation and repitching" section of: http://www.fermentis.com/wp-content/upl ... _EN_HD.pdf

"Recovering yeast after fermentation and repitching is possible if the cell
count is controlled to give the correct yeast pitching levels. In order to
control them, laboratory equipment will be needed. In the same way and
using the same equipment, bacteria can be removed by acid washing in
carefully controlled conditions. In case of repitching, yeast must not be
stored out of beer for long periods, even at low temperatures, as yeast
glycogen levels will fall causing slow fermentations.
Yeast mutation occurs rapidly in brewing environments, repitching can be
a delicate operation and may cause beer quality problems in terms of
flavour, yeast settling, diacetyl absorption.
Effects of repitching can be seen in as few as 3 to 5 brews especially
concerning diacetyl reabsorption. For ale beers that are generally more
flavoursome diacetyl levels are less critical."

[daf]

Well I read it in the most recent edition.

Your posts are great, mate. But can you actually give me an answer as to how yeast can be stored?

[Piscator]

Well I read it in the most recent edition.

Your posts are great, mate. But can you actually give me an answer as to how yeast can be stored?

Hi daf - he has actually...... under beer rather than water. For bottom cropping it is better to leave a little beer in the fermenter after racking off, swill this around to loosen the yeast and collect the slurry with a little beer. For top cropping collect a little green beer at the same time and put the cropped yeast into this.
Water has no protective properties or nutrients - beer is acidic and helps protect the yeast to some extent and has some nutrients so is better than water for this job.

In breweries where top cropping is used the yeast is re-pitched very very soon after harvesting and is not stored as such - storage of harvested yeast is more of a homebrew thing because we are rarely in a position to brew one batch after another in such quick succession.

If you are wanting to store for longer periods you can make a batch for bottling to recover yeast from later or for extended storage then you are into the territory of slants etc.

Cheers
Steve

[daf]

Cheers, understand now.

[YeastWhisperer]

Steve is correct. Yeast should be stored under beer. That's what I was attempting to explain with my posts. Steve is also correct about long-term yeast storage. Crops are good for a few months at best. The solution to long-term storage in a home environment is agar slants (slopes). The term agar slant is kind of a misnomer because agar provides little in the way of nutrient. Agar is a plant-based gelatin that is used to solidify a liquid medium; thereby, turning a liquid into a solid. The yeast cells actually grow on the surface of a slant. The easiest solid medium to make is solidified wort. I used solidified wort for many years with very good results. I switched to using a laboratory medium called MYGP mid-last year in order to see if I can extend the period of time that yeast remains viable on slant before needing to be sub-cultured to a new blank slant. MYGP stands for Malt extract, Yeast extract, Glucose, and Peptone.

Here are few photos of slants in my bank that I shot early last year:








I do not know if the piece of lab glassware shown in the photos is available in the UK. This type of glassware is known as a screw cap culture tube in the U.S. Many people confuse screw cap culture tubes with vials; however, screw cap culture tubes have deeper caps than vials and round bottoms like test tubes. Screw cap culture tubes are designed for culturing.

[Goulders]

You can get polypropylene tubes on eBay from places like King Scientific. They are autoclavable and that's where I got mine. If you go to the stickies here, there are some threads on yeast techniques, including making slants (which includes within it a link for stepping up from a slant).